Method for casting metal



Nov. 13,1945 R. K. HOPKINS METHOD FOR CASTING METAL Filed May 20, 1944 2Sheets-Sheet 1 Nov. 13, 1945. R. K. HOPKINS 2,388,974

METHOD FOR CASTING METAL Filed May 2O, 1944 2 Sheets-Sheet 2 Rabenf w mn r In: @22 1 a 2 Patented Nov. 13, W45

METHOD FGR CASG METAL Robert K. HopkinsJNew York, N. Y., asslgnor to TheM. W. Kellogg Company, New York, N. 3., a corporation of DelawareApplication May 20, 1944, Serial No. 5365711 10 Claims.

The present invention relates to a method for casting articles.

One object of the present invention is to provide a new and improvedcasting method.

Another object is to provide a new and im- I proved method for casting atubular article having a closed end.

A further object is to provide a new and improved method for casting avessel or shell with a dished or convex h'ead.

In the electric fusion process of making ingots, current is dischargedacross a flux submerged gap to create a metal fusing zone in and aroundsaid gap. At the same time, solid metal ingredients are fed into thefusing zone according to the desired analysis of the metal to beproduced.

Another object of the present invention is to provide a new and improvedmethod .for casting articles according to the electric fusion processabove described.

In accordance with certain aspects of the present invention, an outermold is provided conforming to the outer shape of the shell or vessel tobe cast, and having a bottom end wall. Metal isfirst produced and castin the bottcm of the outer mold by the electric fusion process abovedescribed. As the casting metal is produced and deposited inthe outermold, the inner mold oi the shell to be cast is built up progressivelyfrom the center radially outwardly and upwardly by the use of moldsections or blocks. At the same time, the mold assembly is desirablyrotated about a substantially vertical axis to equalize the dis--tribution of the metal deposited in the mold space. In this manner,solidification of the metal deposited in the mold space and thecomposition of said metal can be effectively controlled to form a soundheaded shell casting having the fished physical and metallurgicalcharacter- Various other objects, features and advantages of theinvention will be apparent from the following particular description,and from an inspection of the accompanying drawings, in which:

Fig. l is a vertical diagrammatic section of a mold set-up for carryingout the initial stages of the castingmethod of the present invention;

Fig. 2 is a section of the mold set-up taken on line 2-2 of Fig. 1, buton a reduced scale; and

Figs. 3, 4 and 5 are vertical diagrammatic sections of the mold set-upsimilar to that of Fig. 1, but showing later successive stagesrespectively of the casting method of the present invention.

The invention is shown in the drawings applied to a method of making atubular member with an end wall, and more specifically to a method ofcasting a vessel with a domed or bowl-shaped end wall orhead, such as apressure vessel or autoclave. However, it must be understood, that asfar as certain aspects of the invention are concerned, this invention isapplicable to the casting of articles of various shapes, especiallysym-' metrical ones, and maybe employed, as for example, in themanufacture of gun tubes, solid or hollow shafts and flanged articlessuch as manways.

Referring to the drawings, there is provided an outer mold it, whichconforms with the outer sh'ape of the vessel to be cast, and which isshown with a bowl-shaped floor ll defining the outer contour of theconvex head or end wall of the vessel. This mold it is shown symmetricalwith respect to the vertical axis and circular in internalcross-section. The contour of the mold floor ii is sh'own substantiallyas a, segment of a,

sph'ere, but as far as certain aspects of the invention are concerned,this contour may be of any desired configuration.

To permit repeated use of the mold l0, this mold is made of metal havinghigh heat conductivity such as copper, and is hollowed to allow asuitable, cooling medium such as water to be circulated th'erethrough.The mold Hi is advantageously sectionalized, and for that purpose isshown comprising a floor section 82 and separate wall sections 53stacked on the sides of the floor section, and coniointly defining withthe floor section a mold unit having the necessary internal castingform. Although the mold sections l2 and it are not shown with inlet andoutlet connections for the circulating cooling liquid, it must beunderstood that these are provided and connected into the hollows ofsaid sections in any suitable manner.

During the initial stages of the casting operation, the bottom centersection ifiof theinner mold i5 defining the innercurved periphery of thevessel to be cast is disposed in casting position in the lower centralpart of the outer mold Ill, and is spaced from the bottom of said outermold .by a distance corresponding to the thickness of the vessel head tobe cast. This inner mold section it may be supported in casting positionin the interior oi the outer mold ill in anysuitable manner, as forexample bya series of wires or cables i1, and is shown provided with anouter casting surface is extending substantially parallel to orconcentric with the mold floor ll. However, in

- cate, aluminum silicate or glass.

accordance with certain aspects of the present invention, this outercasting surface may directionally vary with respect to the surface ofthe mold floor H, to produce a head or end wall of varying thickness onthe vessel to be cast. i

The inner mold section I6 is desirably made of a construction which willpermit its repeated use. For that purpose thi inner mold section It ismade of metal having high heat conductivity such as copper, and ishollowed to permit circulation of a cooling medium such as watertherethrough; Inlet and outlet connections 22 and 23 on this inner moldsection [8 are connected to inlet and outlet manifolds 24 and 25respectively, desirably through flexible hose connections.

Although the inner mold section It is shown as made of one annularpiece, thi mold section may be made into segments which are bolted orotherwise fastened together to form a single annular unit. Suchfastening means should not be disposed in any position which willdestroy the continuity-of the lower mold surface N or the outerperipheral surface of the mold section It.

For producing and depositing casting metal of the desired analysis inthe interior of the outer mold Ill, the inner mold section [6 isprovided with a central aperture 2'! in'which centrally extends aconsumable electrode 28. Electrode 28 has its lower end submerged in-alayer of flux 30, and is spaced at this end from the molten depositedmetal 3! by a flux submerged gap 32 through which electric current isdischarged to create a metal fusing zone in and around said gap. Toproduce the necessary current discharge across the gap 32, the electrode28 and the mold deposited casting metal 3! are connected in the samecircuit. The necessary electrical connection to the deposited castingmetal M can be effected through the metal walls of the outer mold III,as for example, through a stationary brush contact 33.

The electrode 28 contains at least some of the ingredients of thecasting metal to be produced. Other ingredients may be fed in granular,pellet or pulverulent form into the metal fusing zone created'in andaround gap 32. For feeding the, fluent metal ingredients into the metalfusing zone, electrode 28 may be tubular, and the into maintain thecurrent discharge gap 32 substantially constant in length. The upwardmovement of the electrode 28 may be efiected by,

mounting said electrode with its feeding means on a suitable carriage 38movable vertically, as for example, through cables or feed screws (notshown).

While metal is being produced and deposited in thecenter of the innermold l0 through the electrode 28, any number of other electrode 3! maybe employed (four being shown) on the outside of said inner mold sectionaccording to the size of the vessel to be produced. These outerelectrodes 31 may have their lower ends submerged in the flux 30, andoperate in conjunction with fluent metal ingredients as does the centerelectrode 28, to produce and deposit metal on the outside of the innermold section 8.

As the metal is being produced and deposited in the outer mold In in themanner indicated, mold l0 and the inner mold section l6 are slowlyrotated in unison with respect to the electrodes 31 in order to effecteven distribution of the deposited metal in said outer mold. The moldassembly may be rotated in any suitable manner.

For example, it may be supported on a platform 40 which is secured to averticalshaft 4i driven through a worm and worm wheel drive (not 40 forma continuation of the center inner mold gredients may be fed into thefusion zone through the hollow of the electrode. Electrode 28 may becontinuously formed from a skelp as it is bein consumed.

As the electrode metal is consumed, the electrode 28 is fed downwardlyby any suitable means, indicated diagrammatically by the feed rolls 34,to maintain the gap 32 substantially constant in length.

The flux layer 30 floats out impurities in the metal and conserves theheat in said metal. This flux layer 30 may be of any suitablecomposition well-known in the metallurgical art, and may, for example,comprise silicates or components of silicates, such as magnesiumsilicate, calcium sili- Since the metal producing operation is initiatedwith the electrode 28 close to the bottomof the outer mold I0 during thefirst stages of operation, and since the metal 31 produced and depositedin the-outer mold gradually rises during the operation, it is necessaryto move the electrode upwardly to keep it spaced from the rising. levelof metal 3|. The downward feeding of the electrode28as it isconsumed,and the upward movement of said electrode to compensate for rise in thelevel of the 'depositedmetal 3| are correlated section l6, and isconnected to the manifolds 24 and 25 of the water circulatin systemthrough appropriate hose connections. While the second mold section 45is being set in casting position, the metal producing operation of theelectrodes 31 may be temporarily discontinued, but it is desirable tohave their operation continue during this mold assembly phase as long asthey are positioned away from t e first inner mold section l6 by adistance sufllciently great to permit the second inner mold section 45to be lowered easily into proper casting position without interferencefrom said electrodes 31.

The inner mold section 45 is annular in shape, and fits snugly aroundthe center mold section IS. The outer peripheral surface of the centermold section i8 is desirably inclined or conical, and the innerperiphery of the second outer mold section 45-is of correspondingconical configuration to mate snugly with said outer peripheral moldsurface. The second inner mold section 45 will thereby seat snugly overand around the first inner mold section It, andwill be retained in fixedcasting position shown in Fi 3 by the inclined or conical interengagingsurfaces of said mold sections, so that no additional support for thesecond mold section is necessary.

With the second mold section 45 supported in casting position shown inFi 3, the outer elecstantially constant in length.

assae'ra outwardly to an approximate position B close to and on theouter side of the prospective position of the third inner mold sectionas to be later' added to the inner mold assembly. While the electrodes37 are moved radially outwardly, they are also moved upwardly to keepapace with. the rising level of the deposited metal at, so that thecurrent discharge flux submerged gaps below said electrodes respectivelyare maintained sub- When the depmited metal 35 reaches the lower outerannular corner of the second inner mold section 65, the third innerannular mold section 48 of hollow copper construction is added to theinner mold assembly as shown in Fig. 4, and in a manner similar to thatdescribed in connection with the addition of the second mold section t5,and said mold section 68 is connected to the manifolds 2d and of thewater circulating system through appropriate hose connections. Duringthis mold assembly stage, the metal producing operations of theelectrodes 3; maybe temporarily discontinued, but these operations arede-' sirably continued as long as enoughspace is available to set thethird inner mold section d8 into proper casting position withoutinterferin with said operations.

- During the stages of the process when the cylindrical portion of thevessel til is being cast, the inner mold sections 52 for this portionare also cylindrical in shape, and are stacked one on top of the other.During this stage of the casting operation, the electrodes 31 are movedmerely vertically in the mold space substantially midway between thesides thereof.

It should be noted that during the process of casting the shell 5! asdescribed, a layer of highly superheated metal is continuouslymaintained in the upper section of the deposited metal. The

highly superheated metal serves to feed the shrinking solidifying metalbeneath it and thereby serves to continuously hot-top the metal as it isprogressively cast. In this manner, a shell cast- I ing is producedwhich is sound and substantially By the time the third inner moldsection $8 is ready .to be set into casting position, the portion of thedeposited metal 3! underneath the first inner mold section It may besolidified, so that the cable supports H for said mold section may bedispensed with.

. After the third inner mold section d8 has been set into proper castingposition, the metal producing operations of the electrodes 37 arecontinued or resumed, and said electrodes are moved upwardly andradially from the position B to the approximate position C shown in Fig.4 in a manner and for the purpose similar to that already described inconnection with the movement of these electrodes from position A to Bshown in Fig. 3.

The two component movements of each electrode bl radially and upwardlyfrom position A to B shown in Fig. 3 may be made simultaneously, so thatby the time the deposited metal ill reaches the lower outer annularcorner oi the second inner mold section 45, these electrodes will be inposition B; However, as far ascertain aspects of the invention areconcerned, the electrodes 31 may be moved only vertically from theposition A, while the first and second-inner mold section It and d5alone are set in casting position, and then after the deposited metal Mhas reached the lower outer annular corner of the second inner moldsection 55, the elevated electrodes may be moved in one step radiallyoutwardly to position B in preparation for the assembly attachment ofthe third innermoldsection d8. Similarly, the electrodes 31 may be movedfrom position B to position C in two distinct steps during the phase ofoperation shown in Fig. 4.

If the movement of the electrodes 37 is eflected simultaneously upwardlyand radially outwardly, said electrodes are always maintainedsubstantially midway oi the horizontal width of the mold space betweenthe outer and inner molds Ill and I5. If the electrodes 31 are movedstep by step as described, the electrode positions A, B, C, etc. will besubstantially midway of the horizontal width of the mold space.

After the deposited metal 3! reaches the lower annular corner of thethird inner mold section 48,

homogeneous throughout its entire length.

As many changes can be made in the above method and apparatus, and manyapparently widely difi'erent embodiments of this invention can be madewithout departing from'the scope of the claims, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. A process of casting a vessel with an end wall, which comprises thesteps of depositing molten metal in an outer mold having side and bottomwalls, and progressively assembling an inner core in and correlativelyto said outer mold from the center of said outer mold radially outwardlyand upwardly as the level of the deposited metal rises, to form betweenthe mold and the core a mold space defining the walls of the vessel tobe cast, and to extend progressively said mold space radially ahead andabove the rising level of the deposited metal.

2. A process of casting a vessel with a convex end wall, which comprisesdepositing molten metal in an outer mold having a cup-shaped moldcavitywith a dished floor, and assembling an inner core in saidouter-mold step by step from the center of said outer mold radiallyoutwardly and upwardly as the level of the deposited metal rises, toform with said outer mold a cup-shaped mold space dished at one end, andto extend progressively said mold space radially ahead and above therising level of the deposited metal.

3. A process of casting a vessel with a convex end wall, which comprisesmbling an inner core radially outwardly'and upwardly in an outer moldhaving a cup-shaped cavity with a dished floor, to form with said outermold a mold space conforming with the shape 01' the end wall of thevessel to be cast, and to extend progressively said mold space radiallyoutwardly and upwardly, and depositing molten metal in said mold spacethrough its outer extended section after each inner mold assemblingstep.

4. A process of casting, comprising producing and depositing moltenmetal in an outer cupshaped mold by the current discharge action of oneor more flux submerged electrodes, and progressively assembling an innercore in said outer mold correlatlvely with respectto said outer mold asthe level of deposited metal increases, to extend the mold space definedbetween said molds progressively ahead oi the deposited metal.

5.-A process of making a vessel with a convex end wall, which comprisesassembling an inner core radially outwardly and upwardly in an outermold having a cup-shaped cavity with a dished floor, to form with saidouter mold a mold space conforming with the shape 0! the end wall or thevessel to be cast, and to extend progressively said mold space radiallyoutwardly and upwardly, and producing and depositing molten metal insaid mold space alter each inner core assembling step by the currentdischarge action or one or'more flux submerged consumable electrodesextending in the outer extended peripheral section '0! said mold space.

8. A process oi casting a hollow article, comprising depositing metal inamold, assembling a core progressively and correlativeiy with respect tosaid mold as the amount oi deposited molten metal increases, to extendprogressively the mold space defined betweed said mold and said coreaheadoi the deposited metal, and rotating said mold and said core inunison as metal is being deposited in said space to sheet substantially?equal distribution oi the deposited metal in said mold sp ce.

'1. A process or casting, comprising depositing molten metal in an outercup-shaped mold, and progressively assemblins an inner core in saidouter mold correlatively with respect to said outer mold as the level ofdeposited metal increases, by adding annular core sections into snugperipheral embracing engagement with previously assembled inner annularcore sections, whereby the mold space defined between said mold and coresections extends progressively ahead of the deposited metal.

in said outer mold by adding annular core sections into snug peripheralembracing engagement with previously assembled inner annular coresections, whereby the mold space defined between said mold and coresections extends progressively ahead of the deposited metal, said coresections having curved surfaces opposite said outer mold tioor blendinginto one substantially continuous surface which extends substantiallyparallel to said outer mold floor.

9. A process 01' making a vessel with a convex end wall, which comprisesdepositing molten metal in a mold space between an outer mold and apartially completed inner core containing a peripheral annular section,adding an annular core section snugly around said last-mentioned annularcore section when the molten metal in said space reaches a substantiallypredetermined level in said space. to extend progressively the moldspace radially outwardly, and repeating said inner core assemblingoperation each time the level or the molten metal reaches asubstantially predetermined level with respect to the last-assembledinner core section.

10. A process of making a vessel with a convex end wall, which comprisesproducing and depositing molten metal by the current discharge action ofone or more tiux submerged electrodes in aaaprocessofcastingavesselwlthaconvcx' end wall, which comprisesdepositing molten metal in an outer cup-shaped mold with a dished curveddoor. and as the level or deposited metal increases, progressivelyassembling an inner core mold space between an outer mold and apartially completed inner liquid-cooled core containing a peripheralannular section, adding an annular liquid-cooled core section snuglyaround said lastmentioned annular core section when the molten metal insaid space reaches a substantially predetermined level in said space toextend progressively the mold space radially outwardly, repeatins saidinner core assembling operation each time the level of the molten metalreaches a substantially predetermined level with respect to thelast-assembled inner core section, and rotating said inner core andouter mold while the metal is being produced and deposited in said moldspace deposited metal in'sald space.

to elect substantially uniform distribution r the i ROBERT K. HOPKB lS.

